Effect of combined polymers on the loss of efficiency caused by mechanical degradation in drag reducing flows through straight tubes

• Published in: Rheologica acta Vol. 55; no. 7; pp. 559 - 569
• Main Authors: B. Sandoval, Gustavo A., Soares, Edson J.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-07-2016; Springer Nature B.V
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Complex Fluids and Microfluidics; Computational fluid dynamics; Degradation; Drag reduction; Efficiency; Ethylene oxide; Food Science; Materials Science; Mechanical Engineering; Original Contribution; Polymer Sciences; Polymers; Soft and Granular Matter; Tubes; Turbulent flow; Water soluble polymers; Xanthan; Drag reduction; Turbulence; Polymer solution
• ISSN: 0035-4511; 1435-1528
• DOI: 10.1007/s00397-016-0927-6

The mechanical molecular degradation in drag reducing flows is a huge problem in the effort to improve the efficiency of drag reducers, which is clearly increased when a combination of materials is used. Here, we analyze mixtures of three kinds of water-soluble polymers: Poly (ethylene oxide) (PEO), Polyacrylamide (PAM), and Xanthan Gum (XG). Two kinds of mixtures are tested: (a) PAM and XG; (b) PEO and XG. The synergy between the polymers is clearly noticeable. The values of the drag reduction (DR) obtained by the polymer–polymer combination was larger than that observed for a single polymer in a solution with the same total concentration of the mixture. Our tests are conducted in straight tubes where the total pressure is fixed. The values of DR are computed step-by-step, as the total amount of solution pass through the system. In doing so, we carefully took into account the loss of efficiency caused by the turbulent flow in the straight tubes. It is quite clear that the degradation of the flexible polymers (PEO and PAM) is delayed in the mixtures. In other words, besides the increase in the DR, the flexible polymers are more resistant when in the presence of the rigid one (XG). Such observation is the main conclusion of this work.